Animated Haed while pressing button

Hi all!

I need your help. Fast!
I’d like to animate a talking head, that opens and closes it mouth while I press space-bar.
I already know how to animate stuff and made a few games, still, with little or no animation. How do I do this easily?
(just for fact, it has to be a textured female head with a black background)

@OrangeLightning is 100% correct. However, you have to make sure you have a model you can actually use first:

You have to make sure that the head model you’re wanting to move actually has a separate jaw bone that can be moved, and even more fundamentally is a skinned mesh with bones in the first place. If you have a model with a bone structure (a bunch of sub-objects like “hip”, “spine1”, etc.), check to see what bones are available in the head. If not, there’s no fast, easy way to do what you want, and you’ll need significant training in a 3D modeling program to skin the mesh before you can do anything.